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[2003:cb:c749:6600:b73a:466c:e610:686]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4364a3766dcsm63707265e9.0.2024.12.19.08.56.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Dec 2024 08:56:55 -0800 (PST) Message-ID: <5fae8eb9-0639-4b1b-aeac-c5adc4172446@redhat.com> Date: Thu, 19 Dec 2024 17:56:54 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/2] s390: Remove uses of page->index To: Matthew Wilcox Cc: Claudio Imbrenda , linux-mm@kvack.org, linux-s390@vger.kernel.org References: <20241219162252.1025317-1-willy@infradead.org> <9d4efc2e-56d9-4786-9ccb-ecd15f34f3e7@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: P5kqYvXBG2mrYaRYkn1UH6UOTdM9i4gROZEkQEn0faI_1734627417 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 9DC1BA0007 X-Stat-Signature: gyihy1d8sfnntsm5tayxzywnsjdkr7jp X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1734627369-924678 X-HE-Meta: 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 Aze+h+B4 Flh7cxNh+5kDS1J487SSYAWoQH9d/XO9iwHXqZVONeSsrKbiE6VMtHM6ScdnwrI9sfxrLGeS8QoX9T4O+bNjleVRYjs/OfzDEVvbc6xoQRjH8M8AQz5XfdlwcZwa3LXLU3g4k6mQ64z9Q7+hxGWrrgh37FYsKMSjrV8LZDmIBNhXZhhcZIusgvii6g8nsML2rNgqVg7oRtZv/qdOqZc6naoGQXzRvO9kXZq1gqH54eTJeE+8TaXVPaXHOCpDGicXspfZKvuizbfROyl4p+5fWUjVx7dDtyeEtFoD4TUDHea3Tx/qZ9xPjXkCunkzM0swRGhG9i+Un+DdGiEfxYtkW/y4+aoJEhHjscE1aa9CfjwTCP8HkYCXgnZcPa78ttyL3dXNYHL5ctggH9YA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.034590, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 19.12.24 17:52, Matthew Wilcox wrote: > On Thu, Dec 19, 2024 at 05:33:32PM +0100, David Hildenbrand wrote: >> On 19.12.24 17:22, Matthew Wilcox (Oracle) wrote: >>> These two patches compile ... I can promise nothing more than that. >>> >>> David suggested to me that the gmap code really should be using ptdesc, >>> and I think I agree with him. The vsie code looks quite different >>> and probably shouldn't be using a ptdesc, but we can use page->private >>> instead of page->index. It's not yet clear to me if we'll ever manage >>> to get rid of page->private. >> >> Just curious, does that mean that memdesc would always contain these >> additional 8 bytes? > > Eventually we'll have a choice to make. > > 1. Shrink struct page to 8 bytes, but we'll need to allocate a 32 byte > memdesc for all the current users of page->private > 2. Shrink struct page to 16 bytes > > I genuinely don't know which will be better for the whole system. > > If you're asking because we can defer some of the mapcount > work by using the 8 bytes of page->private to store mapcount, then > yes, let's do that. Yeah, it could give us a bit more time, until we know that we can just get rid of it in all kernel configs. But let's see if that is still a problem when we're getting closer to removing them. -- Cheers, David / dhildenb